▶This apparatus in used for the rapid in-situ measurement of the structural properties of existing road pavements constructed with unbound materials. Continuous measurements can be made down to a depth of approximately 850 mm or, when extension shafts and rods are used (available as accessories), to a recommended maximum depth of 2 m. Where pavements layers have different strengths the boundaries can be identified and the thickness of the layers determined. Correlations have been established in earlier work (Van Vuuren, Klein and Van Herden, Smith and Pratt) between  the Dynamic Cone Penetrometer (DCP) and California Bearing Ratio (CBR) so that results can be interpreted and compared with CBR specifications.